1. Field of the Invention
The present invention relates to a pharmaceutical composition for prevention or treatment of dementia, which includes shRNA containing a nucleotide sequence of SEQ. ID No. 1 or 2 capable of inhibiting expression of S100a9, as well as a method for prevention or treatment of dementia by administering the foregoing shRNA into cells of mammals including, for example, human beings.
2. Description of the Related Art
It is known that S100a9 is an 5100 family as a calcium-binding protein associated with inflammation. Increase in activated S100a9 in microglia cells activates, signal transduction (or signaling) dependent on mitogen-activated protein kinase (MAPK) cascade, NF-kB or calcium.
Neurodegenerative diseases including cerebral ischemia and Alzheimer's disease have been known to associate with modified expression or function of S100 family members and, recently, S100a9 is known to participate in inflammation of patients with Alzheimer's disease and be considerably increased in neuritic plaques. However, a pathological mechanism regarding the foregoing conditions is still not disclosed.
RNA-mediated interference (RNAi) refers to a phenomenon that an RNA fragment with a size of 21 to 25 nucleotides (nt) is selectively bonded to mRNA having a complementary sequence and degrades the same in order to inhibit protein expression.
Since Elbashir research team reported in 2001 that expression of a particular gene may be selectively inhibited when a short dsRNA with 21 bases (siRNA) is introduced into a cultured mammal cell, applicability of RNAi in mammalian cells was noticeably increased. At present, gene expression inhibitory technologies using siRNA are generally used to understand functions of various genes and are being actively applied to development of drugs for treating incurable diseases such as cancer, infectious diseases, etc.
Induction of cell apoptosis in human myelogenous leukemia cells using siRNA specific to oncogenic genes such as Bcl-2 and c-Raf closely relating to tumor formation, was reported. It was also disclosed that using siRNA specific to Bcr-ab1 fused genes massively expressing in chronic myelogenous leukemia (CML) may remarkably reduce expression of Bcr-abl protein.
Alternatively, approaches for inhibition of viral infection using a complementary siRNA of CXCR4/CCR5RNA, which is a co-receptor of siRNA or HIV-1 complementary to HIV RNA, are being actively studied and developed. In recent years, it was reported that a synthesized siRNA complementary to hepatitis virus may effectively inhibit gene expression of the hepatitis virus.
Such techniques to inhibit expression of particular genes in animal cells using siRNA may include, for example, in vitro preparation of siRNA comprising synthesizing siRNA in vitro and introducing the same into cells. However, the foregoing method has disadvantages in that bio-synthesis of siRNA requires high costs and cell introduction of the synthesized siRNA has relatively low efficacy with regard to cell plasma infection, in turn entailing insufficient gene inhibition using siRNA while exhibiting RNAi effects for 2 to 3 days only. In order to overcome the above problems, a method of introducing a siRNA plasmid vector capable of expressing siRNA into cells was developed.
Especially, an siRNA plasmid vector expressing a short hairpin RNA (shRNA), wherein sense and anti-sense sequences of siRNA target sequence are located from a promoter of RNA polymerase III by interposing a loop having 5 to 9 bases, is characterized in that the shRNA expressed after introduction thereof into cells is transformed into siRNA by an siRNA processing enzyme (that is, Dicer or RNase III) and the transformed siRNA can selectively inhibit expression of specific genes.